微波辅助萃取-气相色谱测定土壤中多氯联苯

建立了微波辅助萃取-气相色谱-微电子捕获检测土壤样品中6种多氯联苯(pcb28, pcb52, pcb101, pcb138, pcb153和pcb180)的方法. 确定了以V(20 mL丙酮):V(正己烷)＝1:1混合溶剂作萃取剂, 萃取温度110 ℃, 仪器功率800 W, 微波萃取5 min的样品前处理条件, 并用柱温程序优化了GC-μECD分析条件. 方法的检出限为0.027～0.087 ng/g; 相对标准偏差为3.4%～7.6% (n=6); 加标平均回收率79.8%～91.1%. 可用于土壤环境中多氯联苯的监测分析.     

Oxidation and flow-injection amperometric determination of 5-hydroxytryptophan at an electrode modified by electrochemically assisted deposition of a sol-gel film with templated nanoscale pores

The oxidation of 5-hydroxytryptophan (5-HTPP) yielded a passivating polymeric film at an indium tin oxide (ITO) electrode. Coating ITO with a nanoscale sol-gel film with a mesoporous structure was shown to change the pathway of the chemical reaction coupled to the electron transfer. The sol-gel film was deposited by an electrochemically assisted process, and the mesoporosity was imparted by including generation-4 poly(amidoamine) dendrimer in the precursor solution. The dendrimer was removed subsequently with an atmospheric oxygen plasma. This electrode remained active during cyclic voltammetry and controlled potential electrolysis of 5-HTPP, which was attributed to dimer, rather than polymer, formation from the oxidation product. Mass spectrometry confirmed this hypothesis. The anodic current was limited by the electron-transfer kinetics. Modification of the sol-gel film by inclusion of cobalt hexacyanoferrate, which catalyzes the oxidation, resulted in a diffusion-limited current. Determination of 5-HTPP by flow-injection amperometry had a detection limit of 17 nM.     

表面活性剂泡沫强化修复污染土壤研究进展

全球土壤资源污染严重,表面活性剂泡沫强化修复技术因泡沫流动受重力影响小、避免淋洗液难控制使区域扩大引发二次污染、修复效果好等备受关注。本文综述了表面活性剂泡沫强化修复技术在治理污染土壤中的研究进展,详细阐述了表面活性剂泡沫强化修复污染物的效果、机理、影响因素及应用前景,并就表面活性剂泡沫强化修复技术今后的研究方向进行了展望。     

Novel solvent‐free microwave‐assisted extraction coupled with low‐density solvent‐based in‐tube ultrasound‐assisted emulsification microextraction for the fast analysis of organophosphorus pesticides in soils

A novel and rapid solventless microwave‐assisted extraction coupled with low‐density solvent‐based in‐tube ultrasound‐assisted emulsification microextraction has been developed for the efficient determination of nine organophosphorus pesticides in soils by GC analysis with microelectron capture detection. A specially designed, homemade glass tube inbuilt with a scaled capillary tube was used as an extraction device to collect and measure the separated extractant phase easily. Parameters affecting the efficiencies of the developed method were thoroughly investigated. From experimental results, the following conditions were selected for the extraction of organophosphorus pesticides from 1.0 g of soil sample to 5 mL of aqueous solution under 226 W of microwave irradiation for 2.5 min followed by ultrasound‐assisted emulsification microextraction with 20 μL toluene for 30 s and then centrifugation at 3200 rpm for 3 min. Detections were linear in the range of 0.25–10 ng/g with detection limits between 0.04 and 0.13 ng/g for all target analytes. The applicability of the method to real samples was assessed on agricultural contaminated soils and the recoveries ranged between 91.4 and 101.3%. Compared to other methods, the present method was shown to be highly competitive in terms of sensitivity, cost, eco‐friendly nature, and analysis speed.     

微波辅助萃取-HG-AFS测定土壤中无机砷

采用微波辅助萃取分析物,联合原子荧光光谱技术,建立了微波辅助萃取-HG-AFS测定土壤中无机砷的分析方法。用正交试验设计结合单因素试验优化了样品粒度、萃取温度、萃取时间、固液比等微波萃取条件,研究了共存离子对无机砷测定的干扰情况。方法的线性范围为1.0~160.0μg/L,无机砷的检出限为0.20μg/L,相对标准偏差为0.3%,样品回收率为93.0%~98.5%。用本法分析3个不同产地有代表性土壤中无机砷量。     

A combined application of thermal desorber and gas chromatography to the analysis of gaseous carbonyls with the aid of two internal standards

In this study, a series of GC calibration experiments were conducted to examine the feasibility of the thermal desorption approach for the quantification of five carbonyl compounds (acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde) in conjunction with two internal standard compounds. The gaseous working standards of carbonyls were calibrated with the aid of thermal desorption as a function of standard concentration and of loading volume. The detection properties were then compared against two types of external calibration data sets derived by fixed standard volume and fixed standard concentration approach. According to this comparison, the fixed standard volume-based calibration of carbonyls should be more sensitive and reliable than its fixed standard concentration counterpart. Moreover, the use of internal standard can improve the analytical reliability of aromatics and some carbonyls to a considerable extent. Our preliminary test on real samples, however, indicates that the performance of internal calibration, when tested using samples of varying dilution ranges, can be moderately different from that derivable from standard gases. It thus suggests that the reliability of calibration approaches should be examined carefully with the considerations on the interactive relationships between the compound-specific properties and the operation conditions of the instrumental setups.     

Ultrasonic assisted headspace single drop micro-extraction and gas chromatography with nitrogen-phosphorus detector for determination of organophosphorus pesticides in soil

This work describes optimization of headspace single drop micro-extraction for extraction of five organophosphorus pesticides; thionazin, sulfotep, dimethoate, disulfoton and parathion in soil. Ultrasound has also been used successfully to improve and accelerate the extraction of the analytes from the sample. The optimized extraction performance was obtained when the experimental parameters were set as follows; 3.0 μL of octanol as extraction solvent, high ionic strength (20% sodium chloride), 1:1 (w/v) sample dilution with water, extraction temperature at 60 °C for 30 min; applying ultrasound and without any pH adjustment. The optimized method was linear over the calibration range (5–200 and 10–300 for different analytes) with limits of detection of 0.1–2.0 ng g⁻¹. The enrichment factor for OPPs was 1.4–12.7 and the method was also reproducible with the relative standard deviations (RSD%) of 2.1–6.9%.     

Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors

Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Automatic thermal desorption in GC analysis of dairy product volatiles

Summary Automatic thermal desorption (ATD) has been evaluated for the analysis of volatile components from dairy products. It has resulted in a fast and reproducible method which needs only a low amount of sample. Volatile components from milk are collected by off-line purging and trapped on cartridges packed which a suitable adsorbent. Cheese samples are submitted to the same process or directly introduced into the cartridges. The desorption step that follows is carried out automatically and on-line with the chromatographic analysis. Repeatability and sensitivity were satisfactory for both types of products.     

Rapid identification of volatile compounds in aromatic plants by automatic thermal desorption — GC-MS

Summary Thermal desorption is a valuable method for the fractionation of plant volatile components, which can be carried out on-line with GC analysis. The use of coupled GC-MS affords additional qualitative information, of special interest for plant species whose composition has not been previously studied. Some examples of the application of automatic thermal desorption, coupled to GC-MS to the identification and characterization of volatile components of plants of different families are given.     

Application of solid phase microextraction for the determination of soil fumigants in water and soil samples

The potential of solid phase microextraction (SPME) for the determination of the soil fumigants 1,3-dichloropropene (1,3-DCP) and methyl isothiocyanate (MITC) in environmental samples such as soil and water samples has been investigated. Direct immersion SPME followed by GC/ECD/NPD analysis allowed the rapid determination of the two fumigants in water samples, with very little sample manipulation, giving an LOD of 0.5 microg L(-1). Precision, calculated as relative standard deviation (RSD) for six replicates at three concentration levels, was found to be lower than 20% at the concentration levels tested. For the analysis of soil samples, headspace (HS)-SPME combined with GC/ECD/NPD analysis has been applied. Quantification using matrix-matched calibration curves allowed determination of both analytes (MITC and 1-3-DCP) with a LOD of 0.1 microg kg(-1) (RSD < 10%) for the two concentration levels assayed (0.02 and 0.2 mg kg(-1)). The HS-SPME procedure developed in this paper was applied to soil samples from experimental green house plots treated with metham-Na, a soil disinfestation agent that decomposes in soil to MITC. The absence of sample manipulation as well as the low solvent consumption in SPME methodology are among the main advantages of this analytical approach.     

毛细管柱气相色谱法测定土壤中的有机氯农药

研究了使用毛细管柱气相色谱法测定土壤中有机氯农药的分离条件、萃取方法、净化方法以及用替代品进行全程质量控制的方法。有机氯农药检出限在 1 .1～ 4.0 μg L之间 ,各化合物保留时间的RSD <0 .1 % ,所测定化合物的质量浓度在 0 .0 0 6～ 0 .2 0mg L范围内 ,各物质校正曲线 (浓度与峰面积 )的相关系数在 0 .992 6～ 0 .9971之间。用正己烷 丙酮 ( 1 1 ) 1 0 0mL超声波萃取 ,有机氯农药的萃取回收率在 96.3%～ 1 1 4% ,RSD为 0～ 1 1 %。用国产硅镁吸附剂净化 ,有机氯农药的回收率在 1 0 0 %～ 1 40 %之间 ,弗罗里硅土的回收率在 1 0 4 %～ 1 33%之间 ,硅镁吸附剂可以替代弗罗里硅土用于样品的净化。     

Advances in the determination of volatile organic solvents and other organic pollutants by gas chromatography with thermal desorption sampling and injection

Summary The problem of the separation of 34 volatile organic chlorinated compounds is solved by using three different GC columns selected according to the needs of the particular separation required. The effect of water vapor contained as moisture in the trapped air on the retention of some characteristic compounds is studied. The influence of dead volumes on trap injection is also studied.Dedicated to Prof. Dr. A. Liberti on the occasion of his 70th birthday.     

Determination of carbon dioxide in gaseous samples by gas diffusion-flow injection

A gas diffusion-flow injection system was developed for the determination of carbon dioxide in gaseous samples. The calibration was based on the use of either gaseous carbon dioxide or aqueous sodium carbonate standards. Gaseous carbon dioxide samples and gaseous or aqueous standards were injected directly into a donor stream of 1.0×10⁻⁴ M H₂SO₄. In the gas diffusion unit, carbon dioxide diffused through a PTFE membrane into an acceptor stream containing a mixed acid/base indicator. The absorbance of the acceptor stream was monitored spectrophotometrically at 554 nm. The calibration plot was linear over the range of 5.00×10² to 1.27×10⁴ μl l⁻¹ with a sample throughput of 28 h⁻¹ and 3.2% R.S.D. ([CO₂]=2.37×10³ μl l⁻¹, n=12). The detection limit was determined as 2.50×10² μl l⁻¹. The flow system was successfully applied to the analysis of several natural gaseous samples and the headspace of milk containers during storage. The flow injection results were found to be statistically indistinguishable at the 95% confidence level from those obtained by gas chromatography using thermal conductivity detection.     

吸附-自动热解析法测定工厂污染空气中的氯乙烯

利用活性炭采样管捕集空气中的氯乙烯 ,以吸附 -热脱附装置自动热解析 ,在 GC-9AM气相色谱仪上用 Chromosorb 10 2 GC柱为固定相、氢火焰测定空气中氯乙烯含量。当采气量为 30 L时 ,检出限为 0 .2μg/m3。     

Comparison of different calibration approaches in the application of thermal desorption technique: A test on gaseous reduced sulfur compounds

In this study, the reliability of thermal desorbing technique was investigated using the gaseous standards of five reduced sulfur compounds (RSCs: hydrogen sulfide, methane thiol, dimethyl sulfide, carbon disulfide, and dimethyl disulfide). A series of calibration experiments for RSCs were performed using gas chromatography (GC) with pulsed flame photometric detector (PFPD) that is interfaced with a thermal desorber (TD) unit. These calibration data were evaluated by means of two contrasting concepts: fixed standard concentration method (FSC: variable volumetric injection of standard gases prepared at a given concentration) and fixed standard volume method (FSV: injection of multiple standards with varying concentrations at a given volume). When the results of both methods were compared, RSCs generally showed enhanced sensitivity with increasing concentration (FSC) and sample loading volume (FSV). This study highlights that TD-based calibration properties are practically undistinguishable between different sample transfer approaches (e.g., FSV and FSC). As a result, the calibration properties of RSCs derived by thermal desorption technique are greatly distinguished from those of direct injection into GC.     

Determination of pesticides in soil samples by solid phase extraction disks

Summary A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C₈ disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detection limits are between 5 and 30 ng g^–1 based on 5 g moist soil sample. The method was validated by comparing it with conventional liquid-liquid extraction.     

土壤中多种有机氯及拟除虫菊酯类农药的GC-ECD测定

气相色谱法同时测定土壤中多种有机氯及拟除虫菊酯类农药。对土壤的分析结果：有机氯农药的检出限0．001～0、003μg／mL，拟除虫菊酯类农药检出限0.008～0．02μg／mL，线性相关系数0．9978～0．9999。用y（石油醚）：V（丙酮）=3：1超声波提取，有机氯农药回收率94．2％～124．0％，相对标准偏差为3．3％～8．8％（n=5）；拟除虫菊酯类农药回收率95．2％～118．3％，相对标准偏差为5．7％～7．1％（n=5）；方法适用于土壤样品中农药残留测定。     

Comparison of perchloroethylene extraction techniques in soil gas survey quantification

Subsurface pollution by volatile organic compounds has emerged as a widespread problem in industrialized countries. This study compares static headspace technique and methanol extraction/purge-and-trap analysis followed by thermal desorption/gas chromatography in attempts for quantification of gas survey results in the determination of these chemicals in soil. Several soils were contaminated with aqueous solution of perchloroethylene (PCE) (140 mg L⁻¹) using a vapor treatment method. Soil spiking took place up to 24 h in desiccator by exposing individual soil samples contained in open 40 mL glass vials to PCE evaporated from the solution. After exposure the samples were stored and analyzed within 2 days. The achieved results strongly suggest that gas extraction can provide quantitative results, regarding PCE concentration in soils, which are not significantly different from liquid based extraction analysis.